Evidence for disease penetrance relating to CNV size: Pelizaeus-Merzbacher disease and manifesting carriers with a familial 11 Mb duplication at Xq22

Clin Genet. 2012 Jun;81(6):532-41. doi: 10.1111/j.1399-0004.2011.01716.x. Epub 2011 Jun 20.


The potential causes for the incomplete penetrance of Pelizaeus-Merzbacher disease (PMD) in female carriers of PLP1 mutations are not well understood. We present a family with a boy having PMD in association with PLP1 duplication and three females who are apparent manifesting carriers. Custom high-resolution oligonucleotide array comparative genomic hybridization (aCGH) and breakpoint junction sequencing were performed and revealed a familial complex duplication consisting of a small duplicated genomic interval (∼56 kb) and a large segmental duplication (∼11 Mb) that resulted in a PLP1 copy number variation gain. Breakpoint junction analysis implicates a replication-based mechanism underlying the rearrangement formation. X-inactivation studies (XCI) showed a random to moderate advantageous skewing pattern in peripheral blood cells but a moderate to extremely skewed (≥90%) pattern in buccal cells. In conclusion, our data show that complex duplications involving PLP1 are not uncommon, can be detected at the level of genome resolution afforded by clinical aCGH and duplication and inversion can be produced in the same event. Furthermore, the observation of three manifesting carriers with a large genomic rearrangement supports the contention that duplication size along with genomic content can be an important factor for penetrance of the PMD phenotype in females.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Chromosomes, Human, X / genetics*
  • Comparative Genomic Hybridization
  • DNA Copy Number Variations*
  • Family
  • Female
  • Gene Duplication
  • Heterozygote
  • Humans
  • Male
  • Mutation
  • Myelin Proteolipid Protein / genetics
  • Pelizaeus-Merzbacher Disease / genetics*
  • Penetrance*
  • Phenotype
  • X Chromosome Inactivation / genetics


  • Myelin Proteolipid Protein
  • PLP1 protein, human